To the Editor: Health care professionals have expressed concerns about the quality and veracity of information individuals receive from Internet-based sources.1 One area of controversy is the use of Internet sites to communicate information on immunization.2 YouTube is a video-sharing Internet Web site created in 2005 that provides free video streaming. It allows users to share multimedia clips that contain information related to the risks and benefits of immunization. To our knowledge, no studies have examined the content of these videos. We conducted a descriptive study to characterize the available information about immunization on YouTube.

Methods

On February 20, 2007, we searched YouTube (www.youtube.com) using the keywords vaccination and immunization. We included all unique videos with English-language content that contained any message about human immunization. We extracted information on the type of video, clip length, and scientific claims made by the video. We measured the users' interaction with these videos using view counts and the viewer reviews indicated by the star-rating system from 1 star (poor) to 5 stars (awesome). Videos were categorized as negative if the main message of the video portrayed immunization negatively (eg, emphasized the risk of immunization, advocated against immunizing, promoted distrust in vaccine science, made allegations of conspiracy or collusion between supporters of vaccination and manufacturers).

Videos were categorized as positive if the central message supported immunization, portraying it positively (eg, described the benefits and safety of immunizing, described immunization as a social good, or encouraged people to receive immunizations). Positive videos were labeled as public service announcements if they were made by governmental agencies or nongovernmental organizations to provide information about immunization as a service to the public. Videos were categorized as ambiguous if they either contained a debate or were ambivalent (ie, a beneficial or social good was countered by negative experiences such as anxious parents and crying infants). The scientific claims made by the videos were classified as substantiated or unsubstantiated/contradicts using as a reference standard the 2006 Canadian Immunization Guide3 and its human papillomavirus (HPV) vaccine and thimerosal updates,4 which were the most current guidelines available at the time of the search. All videos were analyzed independently by 2 researchers (J.K. and V.P.G.) and disagreements were resolved by an arbitrator (K.W.).

Results

We identified and analyzed 153 videos. The weighted κ statistic for agreement on classification of videos was 0.93. Seventy-three (48%) of the videos were positive, 49 (32%) were negative, and 31 (20%) were ambiguous (Table 1). Compared with positive videos, negative videos were more likely to receive a rating, and they had a higher mean star rating and more views. Among the positive videos, public service announcements received the lowest mean (SD) ratings (2.6 [1.6] stars) and the fewest views (median, 213; interquartile range, 114-409). The most commonly discussed vaccine topic was general childhood vaccines (38 videos [25% of the total]). The most commonly discussed specific vaccine was the HPV vaccine (36 videos [24% of the total]); 20 of these were positive, 4 of which were industry-sponsored. Of the HPV vaccine-related videos, 24 specifically referred to Merck or Gardasil.

Of the negative videos, 22 (45%) conveyed messages that contradicted the reference standard. None of the positive videos made scientific statements that contradicted the reference standard. Table 2 lists the 5 most frequent topics and the scientific claims made.

Comment

Approximately half of the videos posted were not explicitly supportive of immunization, and information in negative videos often contradicted the reference standard. The video ratings and view counts suggest the presence of a community of YouTube users critical of immunization. Clinicians therefore need to be aware of Internet video-sharing sites and should be prepared to respond to patients who obtain their health information from these sources.5 The potential use of these sites for effective communication by health professionals should also be considered.